EP2584410B1 - Trägerkern für einen elektronographen-entwickler, träger für einen elektronographen-entwickler und elektronographen-entwickler - Google Patents

Trägerkern für einen elektronographen-entwickler, träger für einen elektronographen-entwickler und elektronographen-entwickler Download PDF

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Publication number
EP2584410B1
EP2584410B1 EP12756991.1A EP12756991A EP2584410B1 EP 2584410 B1 EP2584410 B1 EP 2584410B1 EP 12756991 A EP12756991 A EP 12756991A EP 2584410 B1 EP2584410 B1 EP 2584410B1
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EP
European Patent Office
Prior art keywords
core particles
carrier
carrier core
size distribution
particles
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Application number
EP12756991.1A
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English (en)
French (fr)
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EP2584410A4 (de
EP2584410A1 (de
Inventor
Tomohide Iida
Tomoya Yamada
Takashi Fujiwara
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dowa Electronics Materials Co Ltd
Dowa IP Creation Co Ltd
Original Assignee
Dowa Electronics Materials Co Ltd
Dowa IP Creation Co Ltd
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Publication of EP2584410A1 publication Critical patent/EP2584410A1/de
Publication of EP2584410A4 publication Critical patent/EP2584410A4/de
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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/10—Developers with toner particles characterised by carrier particles
    • G03G9/107—Developers with toner particles characterised by carrier particles having magnetic components
    • G03G9/1075—Structural characteristics of the carrier particles, e.g. shape or crystallographic structure
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/10—Developers with toner particles characterised by carrier particles
    • G03G9/107—Developers with toner particles characterised by carrier particles having magnetic components
    • G03G9/1087—Specified elemental magnetic metal or alloy, e.g. alnico comprising iron, nickel, cobalt, and aluminum, or permalloy comprising iron and nickel
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/10—Developers with toner particles characterised by carrier particles
    • G03G9/107—Developers with toner particles characterised by carrier particles having magnetic components
    • G03G9/108—Ferrite carrier, e.g. magnetite
    • G03G9/1085—Ferrite carrier, e.g. magnetite with non-ferrous metal oxide, e.g. MgO-Fe2O3
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/10—Developers with toner particles characterised by carrier particles
    • G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/10—Developers with toner particles characterised by carrier particles
    • G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
    • G03G9/1131—Coating methods; Structure of coatings
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/10—Developers with toner particles characterised by carrier particles
    • G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
    • G03G9/1132—Macromolecular components of coatings
    • G03G9/1135—Macromolecular components of coatings obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • G03G9/1136—Macromolecular components of coatings obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds containing silicon atoms

Definitions

  • This invention relates to carrier core particles for electrophotographic developer (hereinafter, sometimes simply referred to as “carrier core particles”), carrier for electrophotographic developer (hereinafter, sometimes simply referred to as “carrier”), and electrophotographic developer (hereinafter, sometimes simply referred to as “developer”). More particularly, this invention relates to electrophotographic developer used in copying machines, MFPs (Multifunctional Printers) or other types of electrophotographic apparatuses, carrier core particles and carrier contained in the electrophotographic developer.
  • carrier core particles for electrophotographic developer
  • carrier carrier for electrophotographic developer
  • developer electrophotographic developer
  • Electrophotographic dry developing systems employed in copying machines, MFPs or other types of electrophotographic apparatuses are categorized into a system using a one-component developer containing only toner and a system using a two-component developer containing toner and carrier.
  • toner charged to a predetermined level is applied to a photoreceptor.
  • An electrostatic latent image formed on the photoreceptor is rendered visual with the toner and is transferred to a sheet of paper.
  • the image visualized by the toner is fixed on the paper to obtain a desired image.
  • a predetermined amount of toner and a predetermined amount of carrier are accommodated in a developing apparatus.
  • the developing apparatus is provided with a rotatable magnet roller with a plurality of south and north poles alternately arranged thereon in the circumferential direction and an agitation roller for agitating and mixing the toner and carrier in the developing apparatus.
  • the carrier made of a magnetic powder is carried by the magnet roller.
  • the magnetic force of the magnet roller forms a magnetic brush, which is also called straight-chain like bristles. Agitation produces triboelectric charges that bond a plurality of toner particles to the surfaces of the carrier particles.
  • the magnetic brush abuts against the photoreceptor with rotation of the magnet roller to supply the toner to the surface of the photoreceptor.
  • Development with the two-component developer is carried out as described above.
  • the recently dominating carrier includes carrier core particles that are the core, or the heart of the carrier particles, and coating resin that covers the outer surface of the carrier core particles.
  • the carrier which is a component of the two-component developer, is required to have various functions including: a function of triboelectrically charging the toner by agitation in an effective manner; a toner transferring ability to appropriately transfer and supply the toner to the photoreceptor; and an improved charge transfer rate at which residual charge on the carrier surface after toner has been transferred to a photoreceptor is leaked.
  • the carrier in the developing apparatus is carried by the magnetic force of the magnet roller.
  • carrier scattering occurs, or more specifically, the carrier scatters toward the photoreceptor, resulting in adhesion of the carrier on paper where an image is formed.
  • the volume mean diameter of spherical magnetic carrier core particles is 25 to 45 ⁇ m
  • the mean pore size of the carrier particles is from 10 to 22 ⁇ m
  • the ratio of particles having a diameter of 22 ⁇ m or lower based on a volume size distribution measurement is less than 1%
  • the magnetization in a magnetic field of 1 kOe is 67 to 88 emu/g
  • the difference in magnetization between scattered carrier particles and original carrier particles in a magnetic field of 1 kOe is 10 emu/g or lower.
  • the carrier having such compositions can prevent image degradation caused by hardening of the bristles of the magnetic brush, as well as carrier scattering.
  • PTL 2 discloses carrier for two-component type electrophotographic developer invented to make the magnetic brush flexible to mitigate the adhesion of the carrier to paper and improve the tone reproducibility of images.
  • the volume mean diameter of the carrier particles is set to 15 ⁇ m to 40 ⁇ m
  • the ratio of carrier particles having a diameter less than 22 ⁇ m is set to 1.0% or more
  • the fluidity of the carrier particles is set to 30 sec/50 g to 40 sec/50 g
  • the apparent density of the carrier particles is set to 2.20 g/cm 3 to 2.50g/cm 3 .
  • PTL 2 suggests that the carrier particles composed as described above can mitigate the carrier adhesion and enhance the tone reproducibility of images.
  • the present invention has an object to provide carrier core particles for electrophotographic developer capable of providing high image quality and longevity as well as more reliable reduction of carrier scattering.
  • the present invention has another object to provide carrier for electrophotographic developer capable of providing high image quality and longevity as well as more reliable reduction of carrier scattering.
  • the present invention has yet another object to provide electrophotographic developer capable of providing high image quality and longevity as well as more reliable reduction of carrier scattering.
  • the inventors of the present invention conceived that the requirement specified in PTL 2 is not enough to achieve carrier of developer used in multifunctional machines that have been developed to meet the recent demands for higher speed developing process and longer life.
  • high-speed machines that supply a larger amount of developer per unit time are designed to rotate their development rollers at a higher rate.
  • toner particles smaller to meet the demand for forming high quality images
  • carrier particles smaller.
  • formation of over 10 thousands or 20 thousands of images degrades carrier characteristics. The inventors expected that such degraded carrier may scatter during the high-speed development process even though conventional carrier does not scatter.
  • the carrier particles have a particle size distribution with a certain width.
  • the ratio of the carrier particles having a diameter of 22 ⁇ m or lower in a volume size distribution is set to a predetermined range, or specifically set to 1.0% or higher to achieve flexible magnetic brush in order to prevent carrier scattering.
  • the inventors found that if there are many submicroscopic-size carrier particles, for example, during high-speed development or after long-term development, the carrier may scatter even though the ratio of the carrier particles having a diameter of 22 ⁇ m or lower in the volume size distribution is in the predetermined range. Then, the inventors have reached a conclusion that the number of the submicroscopic-size carrier particles needs to be controlled to fall in a predetermined range in addition to setting the ratio of the carrier particles having a diameter 22 ⁇ m or lower in the volume size distribution into the predetermined range.
  • the carrier core particles for electrophotographic developer according to the present invention includes a core composition expressed by a general formula: M x Fe 3-x O 4 , wherein 0 ⁇ x ⁇ 1, and M denotes at least one kind of metal selected from the group consisting of Mg, Mn, Ca, Ti, Cu, Zn, Sr and Ni as a main ingredient.
  • the carrier core particles have a volume size distribution with a median particle size ranging from 30 ⁇ m to 40 ⁇ m.
  • the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the volume size distribution is from 1.0% to 2.0%.
  • the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in a number size distribution is 10% or lower and is 3.0% or higher.
  • the magnetization of the carrier core particles in an external magnetic field of 79.58x10 3 A/m (1000 Oe) is from 50 Am 2 /kg (emu/g) to 75 Am 2 /kg (emu/g).
  • the inventors For the purpose of achieving high image quality even in the high speed development or long term usage recently demanded, the inventors first controlled the carrier core particles to have a median particle size in the volume size distribution of from 30 ⁇ m to 40 ⁇ m to optimize the median particle size in the volume size distribution.
  • the inventors For the purpose of enhancing the flexibility of the magnetic brush formed with the carrier, suppressing carrier scattering during the process of high-speed development and carrier scattering after long term usage, and optimizing the magnetic property of the carrier, the inventors have created the carrier core particles having particle size distributions including a volume size distribution with a certain width, and have set the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the volume size distribution to 1.0% to 2.0%, set the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in a number size distribution to 10% or lower, but 3.0% or higher, and set the magnetization of the carrier core particles in an external magnetic field of 79.58x10 3 A/m (1000 Oe) to 50 Am 2 /kg (emu/g) to 75 Am 2 /kg (emu/g).
  • the carrier core particles thus controlled can provide high image quality and longevity as well as more reliable reduction of carrier scattering.
  • the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the number size distribution is 8.0% or lower.
  • the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the volume size distribution is 1.0% to 1.5%.
  • the carrier for electrophotographic developer which is used to develop electrophotographic images, includes carrier core particles for electrophotographic developer having a core composition expressed by a general formula: M x Fe 3-x O 4 , wherein 0 ⁇ x ⁇ 1, and M denotes at least one kind of metal selected from the group consisting of Mg, Mn, Ca, Ti, Cu, Zn, Sr and Ni as a main ingredient, and resin that coats the surface of the carrier core particles for electrophotographic developer.
  • the carrier core particles have a volume size distribution with a median particle size ranging from 30 ⁇ m to 40 ⁇ m.
  • the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the volume size distribution is from 1.0% to 2.0%.
  • the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in a number size distribution is 10% or lower and is 3.0% or higher.
  • the magnetization of the carrier core particles in an external magnetic field of 79,58x10 3 A/m (1000 Oe) is from 50 Am 2 /kg (emu/g) to 75 Am 2 /kg (emu/g).
  • electrophotographic developer used to develop electrophotographic images includes carrier and toner that can be triboelectrically charged by frictional contact with the carrier for development of electrophotographic images.
  • the carrier includes carrier core particles having a core composition expressed by a general formula: M x Fe 3-x O 4 , wherein 0 ⁇ x ⁇ 1, and M denotes at least one kind of metal selected from the group consisting of Mg, Mn, Ca, Ti, Cu, Zn, Sr and Ni as a main ingredient, and a resin that coats the surface of the carrier core particles for electrophotographic developer.
  • the carrier core particles have a volume size distribution with a median particle size ranging from 30 ⁇ m to 40 ⁇ m.
  • the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the volume size distribution is from 1.0% to 2.0%.
  • the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in a number size distribution is 10% or lower and is 3.0 or higher.
  • the magnetization of the carrier core particles in an external magnetic field of 79.58x10 3 A/m (1000 Oe) is from 50 Am 2 /kg (emu/g) to 75 Am 2 /kg (emu/g).
  • the carrier core particles for electrophotographic developer, carrier for electrophotographic developer and electrophotographic developer can provide high image quality and longevity as well as more reliable reduction of carrier scattering.
  • carrier core particles according to the embodiment of the invention will be described.
  • the carrier core particles according to the embodiment of the invention are roughly spherical in shape.
  • the diameter and particle size distribution of the carrier core particles according to the embodiment of the invention will be described later.
  • On the surface of the carrier core particles there are fine asperities that are formed mainly in a firing step, which will be described later.
  • Carrier particles according to the embodiment of the invention are also roughly spherical in shape as with the carrier core particles.
  • the carrier particles are made by coating, or covering, the carrier core particles with a thin resin film and have almost the same diameter as the carrier core particles.
  • the surfaces of the carrier particles are almost completely covered with resin, which is different from the carrier core particles.
  • Developer particles according to the embodiment of the invention include the aforementioned carrier particles and toner particles.
  • the toner particles are also roughly spherical in shape.
  • the toner contains mainly styrene acrylic-based resin or polyester-based resin and a predetermined amount of pigment, wax and other ingredients combined therewith.
  • Such toner is manufactured by, for example, a pulverizing method or polymerizing method.
  • the toner particles in use are, for example, about one-seventh of the diameter of the carrier particles.
  • the compounding ratio of the toner and carrier is also set to any value according to the required developer characteristics.
  • Such developer is manufactured by mixing a predetermined amount of the carrier and toner by a suitable mixer.
  • FIG. 1 is a flow chart showing main steps of the method for manufacturing the carrier core particles according to the embodiment of the invention. Along FIG. 1 , the method for manufacturing the carrier core particles according to the embodiment of the invention will be described below.
  • a raw material containing iron and a raw material containing manganese are prepared.
  • the prepared raw materials are formulated at an appropriate compounding ratio to meet the required characteristics, and mixed ( FIG. 1(A) ).
  • the appropriate compounding ratio in this embodiment is set so that the resultant carrier core particles are made at the compounding ratio.
  • the iron raw material making up the carrier core particles according to the embodiment of the invention can be metallic iron or an oxide thereof, and more specifically, preferred materials include Fe 2 O 3 , Fe 3 O 4 and Fe, which can stably exist at room temperature and atmospheric pressure.
  • the manganese raw material can be manganese metal or oxide thereof, and more specifically, preferred materials include Mn metal, MnO 2 , Mn 2 O 3 , Mn 3 O 4 and MnCO 3 which can stably exist at room temperature and atmospheric pressure.
  • Alternative raw material may be made up by calcinating each of the aforementioned raw materials (iron raw material, manganese raw material, etc.) or the raw materials mixed so as to have target composition and pulverizing the calcinated materials.
  • the carrier core particles in this description can include a core composition expressed by a general formula: M x Fe 3-x O 4 , wherein 0 ⁇ x ⁇ 1, and M denotes at least one kind of metal selected from the group consisting of Mg, Mn, Ca, Ti, Cu, Zn, Sr and Ni as a main ingredient.
  • the mixed raw materials are slurried ( FIG. 1(B) ).
  • these raw materials are weighed to make a target composition of the carrier core particles and mixed together to make a slurry raw material.
  • the method for manufacturing the carrier core particles according to the invention requires acceleration of reduction reaction in a part of the firing step, which will be described later.
  • a reduction agent may be further added to the slurry raw material.
  • a preferred reducing agent may be carbon powder, polycarboxylic acid-based organic substance, polyacrylic acid-based organic substance, maleic acid, acetic acid, polyvinyl alcohol (PVA)-based organic substance, or mixtures thereof.
  • Water is added to the slurry raw material that is then mixed and agitated so as to contain 40 wt% of solids or more, preferably 50 wt% or more.
  • the slurry raw material containing 50 wt% of solids or more is preferable because such a material can maintain the strength when it is granulated into pellets.
  • the slurried raw material is granulated ( FIG. 1(C) ).
  • Granulation of the slurry obtained by mixing and agitation is performed with a spray drier. Note that it may be preferable to subject the slurry to wet pulverization before the granulation step.
  • the temperature of an atmosphere during spray drying can be set to approximately 100°C to 300°C. This can provide granulated powder whose particles are approximately 10 to 200 ⁇ m in diameter. In consideration of the final diameter of the particles as a product, it is preferable to filter the obtained granulated powder by a vibrating sieve or the like to remove coarse particles and fine powder for particle size adjustment at this point of time.
  • the granulated material is fired ( FIG. 1(D) ).
  • the obtained granulated powder is placed in a furnace heated to approximately 900°C to 1500°C and fired for 1 to 24 hours to produce a target fired material.
  • the oxygen concentration in the firing furnace can be set to any value, but should be enough to advance ferritization reaction.
  • a gas is introduced and flows in the furnace to adjust the oxygen concentration to from 10 -7 % to 3%.
  • a reduction atmosphere required for ferritization can be made by adjusting the aforementioned reducing agent.
  • the preferable temperature is 900°C or higher. If the firing temperature is 1500°C or lower, the particles are not excessively sintered and can remain in the form of powder upon completion of firing.
  • the amount of oxygen in the core composition can be controlled to be slightly excessive.
  • One of the possible measures of adding a slightly excessive amount of oxygen in the core composition is to set the oxygen concentration during cooling of the core particles in the firing step to a predetermined value or higher.
  • the core particles can be cooled to approximately room temperature in the firing step under an atmosphere at a predetermined oxygen concentration, for example, at an oxygen concentration higher than 0.03%.
  • a gas with an oxygen concentration higher than 0.03% is introduced into the electric furnace and continues flowing during the cooling step. This allows the internal layer of the carrier core particle to contain ferrite with an excess amount of oxygen. If the oxygen concentration of the gas is 0.03% or lower in the cooling step, the amount of oxygen in the internal layer becomes relatively low. Therefore, the cooling operation should be performed in an environment at the aforementioned oxygen concentration.
  • the fired material is coarsely ground by a hammer mill or the like.
  • the fired granules are disintegrated ( FIG. 1(E) ).
  • classification is carried out with a vibrating sieve or the like.
  • the disintegrated granules are classified ( FIG. 1(F) ). Classifying the granules makes it easier to obtain carrier core particles having a desired size in the latter steps.
  • the classified granules undergo oxidation ( FIG. 1(G) ).
  • the surfaces of the carrier core particles obtained at this stage are heat-treated (oxidized) to increase the particle's breakdown voltage to 250 V or higher, thereby imparting an appropriate electric resistance value, from 1 ⁇ 10 6 to 1 ⁇ 10 13 ⁇ cm, to the carrier core particles.
  • Increasing the electric resistance of the carrier core particles through oxidation results in reduction of carrier scattering caused by charge leakage.
  • the granules are placed in an atmosphere with an oxygen concentration of 10% to 100%, at a temperature of 200°C to 700°C, for 0.1 to 24 hours to obtain the oxidized carrier core particles. More preferably, the granules are placed at a temperature of 250°C to 600°C for 0.5 to 20 hours, further more preferably, at a temperature of 300°C to 550°C for 1 to 12 hours. Note that the oxidation step is optionally executed when necessary.
  • the carrier core particles oxidized as described above are screened by a vibrating sieve or the like to adjust the median particle size or the like so that the carrier core particles have a volume size distribution with a median particle size ranging from 30 ⁇ m to 40 ⁇ m, the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the volume size distribution is from 1.0% to 2.0%, the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in a number size distribution is 10% or lower and is 3.0 or higher, and the magnetization of the carrier core particles in an external magnetic field of 79.58x10 3 A/m (1000 Oe) is from 50 Am 2 /kg (emu/g) to 75 Am 2 /kg (emu/g) ( FIG. 1(H) ).
  • the oxidized carrier core particles are screened several times by a plurality of sieves having different opening sizes to obtain carrier core particles whose median particle size value in the volume size distribution and magnetization value in an external magnetic field of 79.58x10 3 A/m (1000 Oe) fall within the aforementioned range.
  • the carrier core particles for electrophotographic developer according to the embodiment of the invention are specifically carrier core particles including a core composition expressed by a general formula: M x Fe 3-x O 4 , wherein 0 ⁇ x ⁇ 1, and M denotes at least one kind of metal selected from the group consisting of Mg, Mn, Ca, Ti, Cu, Zn, Sr and Ni as a main ingredient, wherein the carrier core particles have a volume size distribution with a median particle size ranging from 30 ⁇ m to 40 ⁇ m, the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the volume size distribution is from 1.0% to 2.0%, the ratio of carrier core particles having a diameter of 22 ⁇ m or lower in the number size distribution is 10% or lower and is 3.0% or higher, and the magnetization of the carrier core particles in an external magnetic field of 79.58x10 3 A/m (1000 Oe) is from 50 Am 2 /kg (emu/g) to 75 Am
  • FIG. 2 is a graph showing two patterns of volume size distributions of carrier core particles.
  • the vertical axis represents ratios (%) in the volume size distribution, while the horizontal axis represents volume diameters ( ⁇ m).
  • the volume size distribution of carrier core particles indicated by a dot and dash line 11 and the volume size distribution of carrier core particles indicated by a double-dot and dash line 12 have the same median particle size of A 1 , and also contain smaller particles having a diameter of A 2 at the same ratio of B 1 in the volume size distributions.
  • the two patterns of the volume size distribution have different areas in the field of smaller particles having a diameter of A 2 or lower. This shows that the number of the smaller carrier core particles having a diameter of less than A 2 is different between the two patterns. More specifically, the graph shows that the number of the carrier core particles indicated by the double-dot and dash line 12 is greater than that of the carrier core particles indicated by the dot and dash line 11.
  • carrier containing a larger number of small carrier core particles having a diameter of less than A 2 forms a magnetic brush of carrier particle groups containing a slightly large number of submicroscopic-size carrier core particles that cannot provide necessary retentivity to retain a magnet roller during high-speed developing process.
  • Such carrier will scatter during the high-speed developing or other processes.
  • defining a range in the number size distribution in addition to defining a range in the volume size distribution can provably prevent carrier scattering.
  • the carrier core particles obtained in the aforementioned manner are coated with resin ( FIG. 1(I) ).
  • the carrier core particles obtained according to the present invention are coated with silicone-based resin, acrylic resin or the like.
  • carrier for electrophotographic developer according to the embodiment of the invention is achieved.
  • the silicone-based resin, acrylic resin or other coating materials can be coated through a well-known coating method.
  • the carrier for electrophotographic developer according to the embodiment of the invention which is used to develop electrophotographic images, includes the above-described carrier core particles for electrophotographic developer and resin coating the surface of the carrier core particles for electrophotographic developer.
  • the carrier for electrophotographic developer including the thus-structured carrier core particles can provide high image quality and longevity as well as more reliable reduction of carrier scattering.
  • the carrier thus obtained and toner in predetermined amounts are mixed ( FIG. 1(J) ).
  • the carrier which is obtained through the above mentioned manufacturing method, for the electrophotographic developer according to the embodiment of the invention is mixed with an appropriate well-known toner.
  • the carrier and toner are mixed by any type of mixer, for example, a ball mill.
  • the electrophotographic developer according to the embodiment of the invention is used to develop electrophotographic images and includes the above-described carrier for electrophotographic developer and toner that can be triboelectrically charged by frictional contact with the carrier for development of electrophotographic images.
  • the electrophotographic developer including the thus-structured carrier for electrophotographic developer can provide high image quality and longevity as well as more reliable reduction of carrier scattering.
  • the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the number size distribution is set to 10% or lower; however, ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the number size distribution can be set to 8.0% or lower. Setting the ratio to 8.0% or lower can achieve carrier core particles that can more reliably provide high image quality and longevity as well as more reliable reduction of carrier scattering.
  • the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the number size distribution can be set to 3.0% or higher. Setting the ratio to 3.0% or higher can make the magnetic brush flexible in a certain extent.
  • Such carrier core particles can be obtained by screening with a sieve a fewer number of times with an improved yield, thereby bringing down manufacturing cost and providing other merits.
  • the ratio of the carrier core particles in the number size distribution can be spedified in terms of carrier core particles having a diameter of, for example, 26 ⁇ m or lower. More specifically, the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the number size distribution is set to be 10% or lower; however, the ratio of the carrier core particles having a diameter of 26 ⁇ m or lower in the number size distribution can be set to 30% or lower.
  • the carrier can be set to contain carrier core particles at the ratio.
  • the ratio of the carrier core particles having a diameter of 22 ⁇ m or lower in the number size distribution set to 8.0% or lower
  • the ratio of the carrier core particles having a diameter of 26 ⁇ m or lower in the number size distribution can be set to 25% or lower.
  • the carrier can be set to contain carrier core particles at the ratio.
  • the slurry was sprayed into hot air of approximately 130°C by a spray dryer and turned into dried granulated powder. At this stage, granulated powder particles out of the target particle size distribution were removed by a sieve. The remaining granulated powder was placed in an electric furnace and fired at 1130°C for 3 hours. During firing, gas was controlled to flow in the electric furnace such that the atmosphere in the electric furnace was adjusted to have an oxygen concentration of 0.8%. The obtained fired material was disintegrated and then classified by a sieve, thereby obtaining carrier core particles whose average particle diameter was 35 ⁇ m. The obtained carrier core particles were held at 470°C for 1 hour under atmospheric pressure to be oxidized.
  • oxidized carrier core particles were screened by a vibrating sieve or the like to adjust the median particle size and so on, resulting in carrier core particles according to Example 1.
  • Carrier core particles of Examples 2 to 8 and Comparative examples 1 to 4 went through the same steps to the adjustment step and have magnetic characteristics and electrical characteristics shown in Table 1.
  • the Mn content in the carrier core particle was quantitatively analyzed in conformity with a ferromanganese analysis method (potential difference titration) shown in JIS G1311-1987.
  • the Mn contents of the carrier core particles described in this invention are quantities of Mn that were quantitatively analyzed through the ferromanganese analysis method (potential difference titration).
  • Microtrac Model 9320-X100 produced by NIKKISO CO., LTD. was used.
  • silicone resin (SR2411 produced by Dow Corning Toray Co., Ltd.) was diluted with toluene solvent to obtain a silicone resin solution containing 2.0 wt% of silicone resin. Then, alumina was added to the silicone resin solution containing 2.0 wt% of resin to obtain a coating resin solution that was then loaded to an immersion type coating machine. The carrier core particles obtained above were heated and then agitated at 240°C for two hours with the coating resin solution in the coating machine, resulting in carrier according to Example 1.
  • the carrier and toner of approximately 5 ⁇ m in diameter were mixed for a predetermined time period by a pot mill to obtain two-component type electrophotographic developer according to Example 1.
  • the two-component type electrophotographic developer was tested with a digital reversal development type test machine operable at a copy speed of 60 copies per minute to evaluate carrier scattering and image quality.
  • Carrier and electrophotographic developer of Examples 2 to 8 and Comparative examples 1 to 4 were obtained through the same manner.
  • the two-component electrophotographic developers were evaluated in terms of carrier scattering. Specifically, the carrier scattering (white spots) present on an image was ranked on three levels as follows. The results are shown in Table 1.
  • Table 1 shows that the carrier core particles of Examples 1 to 8 have distributions and characteristics within the aforementioned ranges. Specifically, the carrier core particles of Examples 1 to 8 have volume size distributions with a median particle size in a range from 30 ⁇ m to 40 ⁇ m, the ratios of the carrier core particles having a diameter of 22 ⁇ m or lower in the volume size distributions are from 1.0% to 2.0%, the ratios of the carrier core particles having a diameter of 22 ⁇ m or lower in the number size distribution are 10% or lower, and the magnetization values of the carrier core particles in an external magnetic field of 1000 Oe are from 50 emu/g to 75 emu/g. In the performance by an actual machine, the carrier core particles do not cause carrier scattering, but provide good image quality both at the initial operation stage and after printing 10 K (K: 1000) sheets of paper.
  • the carrier core particles of Comparative example 1 contain 2.21% particles having a diameter of 22 ⁇ m or lower in the volume size distribution, and contain 11.68% particles having a diameter of 22 ⁇ m or lower in the number size distribution.
  • the carrier core particles of Comparative example 2 contain 0.95% particles having a diameter of 22 ⁇ m or lower in the volume size distribution.
  • the carrier core particle of Comparative example 3 contains 10.76% particles having a diameter of 22 ⁇ m or lower in the number size distribution.
  • the carrier core particles of Comparative example 4 have a volume size distribution with a median particle size of 41.10 ⁇ m and magnetization of 48.3 emu/g in an external magnetic field of 1000 Oe.
  • the developers of Comparative examples 1 to 4 have at least a performance problem in carrier scattering or image quality at the initial operation stage or after 10 K (K: 1000)-sheet printing.
  • the carrier core particles, carrier and electrophotographic developer according to the invention can provide high image quality and longevity as well as more reliable reduction of carrier scattering.
  • the raw material may further include magnesium and calcium.
  • the carrier core particles include a core composition expressed by a general formula: M x Fe 3-x O 4 (0 ⁇ x ⁇ 1, M denotes at least one kind of metal selected from the group consisting of Mg, Mn, Ca, Ti, Cu, Zn, Sr and Ni) as a main ingredient.
  • a preferable example of the raw material containing magnesium to be added is magnesium metal or oxide thereof. More specifically, for example, MgCO 3 , which is magnesium carbonate, Mg(OH) 2 , which is magnesium hydroxide, and MgO, which is magnesium oxide, are preferable.
  • MgCO 3 which is magnesium carbonate
  • Mg(OH) 2 which is magnesium hydroxide
  • MgO which is magnesium oxide
  • 2.3 kg of MgFe 2 O 4 average particle diameter: 3 ⁇ m
  • in addition to 13.7 kg of Fe 2 O 3 average particle diameter: 1 ⁇ m
  • 6.5 kg of Mn 3 O 4 average particle diameter: 1 ⁇ m
  • the carrier core particles containing magnesium in addition to manganese and iron have a magnetization value of approximately 52 emu/g to 54 emu/g in an external magnetic field of 1000 Oe.
  • the content of Mg, Ca or other ingredients is analyzed as follows.
  • the carrier core particles of the invention were dissolved in an acid solution and quantitatively analyzed with ICP to determine the contents of Mg and Ca.
  • the contents of Mg and Ca in the carrier core particles described in this invention are quantities of Mg and Ca that were quantitatively analyzed with the ICP.
  • the oxygen concentration during the cooling operation in the firing step in this embodiment is set to be higher than a predetermined concentration value in order to add an excess amount of oxygen to the carrier core particles; however, the present invention is not limited thereto.
  • an excess amount of oxygen can be added to the carrier core particles by adjusting the compounding ratio of the raw materials in the mixing step.
  • oxygen can be excessively added to the carrier core particles by performing a step of accelerating the sintering reaction, which is executed before the cooling step, under the same atmosphere as in the cooling step.
  • the carrier core particles for electrophotographic developer, carrier for electrophotographic developer and electrophotographic developer according to the invention can be effectively used when applied to copying machines or the like that require high speed development, longevity and high image quality.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • Metallurgy (AREA)
  • Developing Agents For Electrophotography (AREA)

Claims (8)

  1. Trägerkernpartikel für einen elektrofotografischen Entwickler, aufweisend eine Kernzusammensetzung, die durch die allgemeine Formel ausgedrückt ist:
    Mx Fe3-xO4, wobei 0 ≤ x ≤ 1, und M mindestens eine Art von Metall bezeichnet, und zwar gewählt aus der Gruppe, die aus Mg, Mn, Ca, Ti, Cu, Zn, Sr und Ni als Hauptbestandteile besteht, wobei
    die Trägerkernpartikel eine volumenbezogene Größenverteilung mit einer mittleren Partikelgröße zwischen 30 µm bis 40 µm aufweisen,
    wobei der Anteil der Trägerkernpartikel, die einen Durchmesser von 22 µm oder weniger aufweisen, bei der volumenbezogenen Größenverteilung zwischen 1,0 % und 2,0 % liegt, und eine Magnetisierung der Trägerkernpartikel in einem externen Magnetfeld von 79,58 x 103 A/m (1000 Oe) zwischen 50 Am2/kg (emu/g) und 75 Am2/kg (emu/g) beträgt,
    dadurch gekennzeichnet, dass der Anteil der Trägerkernpartikel, die einen Durchmesser von 22 µm oder weniger aufweisen, bei einer anzahlbezogenen Größenverteilung 10 % oder weniger, und 3,0 % oder mehr beträgt.
  2. Trägerkernpartikel für einen elektrofotografischen Entwickler nach Anspruch 1, wobei der Anteil der Trägerkernpartikel, die einen Durchmesser von 22 µm oder weniger aufweisen, bei der anzahlbezogenen Größenverteilung 8,0 % oder weniger beträgt.
  3. Trägerkernpartikel für einen elektrofotografischen Entwickler nach Anspruch 1, wobei der Anteil der Trägerkernpartikel, die einen Durchmesser von 22 µm oder weniger aufweisen, bei dervolumenbezogenen Größenverteilung von 1,0 % bis 1,5 % beträgt.
  4. Trägerkernpartikel für einen elektrofotografischen Entwickler nach Anspruch 1, wobei die Oberfläche der Trägerkernpartikel oxidiert ist, wodurch ein elektrischer Widerstandswert von 1 x 106 bis 1 x 1013 Ω x cm erteilt wird, um die Durchbruchspannung der Partikel auf 250 V oder mehr zu vergrößern.
  5. Träger für elektrofotografischen Entwickler, der zum Entwickeln von elektrofotografischen Bildern verwendet wird, aufweisend:
    Trägerkernpartikel für einen elektrofotografischen Entwickler, aufweisend eine Kernzusammensetzung, die durch die allgemeine Formel ausgedrückt ist: Mx Fe3-xO4, wobei 0 ≤ x ≤ 1, und M mindestens eine Art von Metall bezeichnet, und zwar gewählt aus der Gruppe, die aus Mg, Mn, Ca, Ti, Cu, Zn, Sr und Ni als Hauptbestandteile besteht, wobei die Trägerkernpartikel eine volumenbezogene Größenverteilung mit einer mittleren Partikelgröße zwischen 30 µm bis 40 µm aufweisen, wobei der Anteil der Trägerkernpartikel, die einen Durchmesser von 22 µm oder weniger aufweisen, bei der volumenbezogenen Größenverteilung zwischen 1,0 % und 2,0 % liegt, der Anteil der Trägerkernpartikel, die einen Durchmesser von 22 µm oder weniger aufweisen, bei einer anzahlbezogenen Größenverteilung 10 % oder weniger, und 3,0 % oder mehr beträgt, und eine Magnetisierung der Trägerkernpartikel in einem externen Magnetfeld von 79,58 x 103 A/m (1000 Oe) zwischen 50 Am2/kg (emu/g) und 75 Am2/kg (emu/g) beträgt, und
    ein Harz, das die Oberfläche der Trägerkernpartikel für einen elektrofotografischen Entwickler beschichtet.
  6. Träger für elektrofotografischen Entwickler, der zum Entwickeln von elektrofotografischen Bildern verwendet wird, nach Anspruch 5, wobei die Oberfläche der Trägerkernpartikel oxidiert ist, wodurch ein elektrischer Widerstandswert von 1 x 106 bis 1 x 1013 Ω x cm erteilt wird, um die Durchbruchspannung der Partikel auf 250 V oder mehr zu vergrößern.
  7. Elektrofotografischer Entwickler, der zum Entwickeln von elektrofotografischen Bildern verwendet wird, aufweisend:
    Trägerkernpartikel für einen elektrofotografischen Entwickler, aufweisend eine Kernzusammensetzung, die durch die allgemeine Formel ausgedrückt ist:
    Mx Fe3-xO4, wobei 0 ≤ x ≤ 1, und M mindestens eine Art von Metall bezeichnet, und zwar gewählt aus der Gruppe, die aus Mg, Mn, Ca, Ti, Cu, Zn, Sr und Ni als Hauptbestandteile besteht, wobei die Trägerkernpartikel eine volumenbezogene Größenverteilung mit einer mittleren Partikelgröße zwischen 30 µm bis 40 µm aufweisen, wobei der Anteil der Trägerkernpartikel, die einen Durchmesser von 22 µm oder weniger aufweisen, bei der volumenbezogenen Größenverteilung zwischen 1,0 % und 2,0 % liegt, der Anteil der Trägerkernpartikel, die einen Durchmesser von 22 µm oder weniger aufweisen, bei einer anzahlbezogenen Größenverteilung 10 % oder weniger, und 3,0 % oder mehr beträgt, und eine Magnetisierung der Trägerkernpartikel in einem externen Magnetfeld von 79,58 x 103 A/m (1000 Oe) zwischen 50 Am2/kg (emu/g) und 75 Am2/kg (emu/g) beträgt, und ein Harz, das die Oberfläche der Trägerkernpartikel für einen elektrofotografischen Entwickler beschichtet; und einen Toner, der durch Reibungskontakt mit dem Träger triboelektrisch geladen werden kann, zur Entwicklung von fotografischen Bildern.
  8. Elektrofotografischer Entwickler, der zum Entwickeln von elektrofotografischen Bildern verwendet wird, nach Anspruch 7, wobei die Oberfläche der Trägerkernpartikel oxidiert ist, wodurch ein elektrischer Widerstandswert von 1 x 106 bis 1 x 1013 Ω x cm erteilt wird, um die Durchbruchspannung der Partikel auf 250 V oder mehr zu vergrößern.
EP12756991.1A 2011-03-16 2012-03-01 Trägerkern für einen elektronographen-entwickler, träger für einen elektronographen-entwickler und elektronographen-entwickler Active EP2584410B1 (de)

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JP2011057533A JP5977924B2 (ja) 2011-03-16 2011-03-16 電子写真現像剤用キャリア芯材の製造方法、電子写真現像剤用キャリアの製造方法、および電子写真現像剤の製造方法
PCT/JP2012/055189 WO2012124484A1 (ja) 2011-03-16 2012-03-01 電子写真現像剤用キャリア芯材、電子写真現像剤用キャリア、および電子写真現像剤

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EP2584410A4 (de) 2014-09-03
US9034552B2 (en) 2015-05-19
HK1178267A1 (zh) 2013-09-06
US20130344431A1 (en) 2013-12-26
JP2012194307A (ja) 2012-10-11
EP2584410A1 (de) 2013-04-24
CN102971676B (zh) 2016-01-20
KR101440209B1 (ko) 2014-09-12
JP5977924B2 (ja) 2016-08-24
KR20130031859A (ko) 2013-03-29
WO2012124484A1 (ja) 2012-09-20
CN102971676A (zh) 2013-03-13

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